1. Field of the Invention
This invention is particularly concerned with ventricular assist devices for cardiac output supplementation most optimally useful in a failing heart in sinus rhythm or for effecting increased cardiac output in the dysrhythmic heart, as well as in event of total arrest or ventricular fibrillation.
2. Description of the Prior Art
In the art of mechanical ventricular assistance a cannula-pump left ventricular assist system developed by Peters and co-workers at the University of Utah requires withdrawal of the blood from the left ventricular apex by means of an external roller pump and outflow blood filter and return to the ascending aorta. Transapical left ventricular bypass with local heparinization has also been used by Taguchi and co-workers in Hiroshima, Japan. Cannulation systems with centrifugal pumps have been employed by Pennington and associates in St. Louis. These and other systems have been described at pages 1168 to 1184 in the publication entitled Thoracic & Cardiovascular Surgery, 1983 4Ed by William Glenn, Editor. However, these systems require withdrawal of the blood by pump means which entails the ever present problems of trauma to blood cellular elements and resulting hemolytic effects.
It is also known that devices have been proposed for massaging the heart under certain circumstances that require such action during surgical procedures to restore a heart to its normal function. Since massaging has been known to be required for long periods of time, a device adapted to fit a human heart can be used to apply a rhythmic pulsating pressure to keep the heart pumping for maintaining a supply of blood at the needed pressure to effect circulation. Such devices have been disclosed by Vineberg in U.S. Pat. 2,826,193 of Mar. 11, 1958 and in the U.S. Pat. of Hewson 3,034,501 of May 15, 1962 for an inflatable heart massager in the form of a flexible distendable resilient bag with inner and outer walls of differing thickness, with the outer wall being thicker to minimize relative distending of this wall. It is also disclosed that the interior of the bag can be divided into two chambers so each can have its own supply of pressure fluid.
Another form of heart massage apparatus is disclosed by Goetz in U.S. Pat. 4,048,990 issued Sept. 20, 1977. Here a cup-like inflatable bladder surrounds the heart and is supplied with pressure pulses. A basket-like support is provided for holding the bladder in an operational position around the heart, with the basket-like support on the outside of the bladder.